Filter and filter media having reduced restriction

ABSTRACT

A pleated filter media comprises a plurality of pleats comprised of pleat segments extending in an axial direction between first and second axial ends and extending in a transverse direction that is perpendicular to the axial direction between first and second sets of pleat tips at least partially defined by first and second sets of bend lines. Axial flow channels are defined between the pleat segments in the lateral direction and the plurality of pleats has a width in the transverse direction that varies along the axial direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 14/498,257, filed Sep. 9, 2014, which is a continuation of co-pending U.S. patent application Ser. No. 13/222,880, now U.S. Pat. No. 8,852,310, issued Oct. 7, 2014, entitled “Filter and Filter Media Having Reduced Restriction,” filed on Aug. 31, 2011, which claims the benefit of and priority to U.S. Provisional Application No. 61/380,407, filed Sep. 7, 2010. All of these applications are hereby incorporated herein by reference in their entireties and for all purposes.

FIELD

The present disclosure relates to filters and filter media for filtering fluid, which can be a liquid or a gas, such as air. Such filters are commonly used for example with internal combustion engines but can be used in various other fluid-filtering applications.

BACKGROUND

U.S. Pat. No. 6,391,076, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a full flow fluid filter having a housing extending axially along an axis, and a pleated filter element having a plurality of pleats in a closed loop annulus having an outer perimeter defined by a plurality of outer pleat tips, an inner perimeter defined by a plurality of inner pleat tips, and a hollow interior extending along the axis. Fluid flows substantially directly axially through the filter element, with minimal bending and change of direction, minimizing flow restriction.

U.S. Patent Publication No. 2006/0065592, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a direct flow filter having seal tips alternately sealing upstream and/or downstream ends of wall segments to each other to define first and second sets of flow channels and protecting the ends of the wall segments from damage, including upstream ends from incoming debris, and providing structural support withstanding high flow rates and improving flow by means of the geometry of the seal.

U.S. Pat. No. 7,314,558, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a pleated panel fluid filter filtering fluid flowing along an axial flow direction and includes angled panels and/or progressively increasing flow channel width and/or skewed panel projections and/or flattened pleat tip bend lines.

U.S. Pat. No. 7,323,106, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a filter with multiple pleated filter elements having axially extending channels having a transverse pleat channel height and a lateral channel width. The pleated filter elements have different channel heights.

U.S. Pat. No. 7,540,895, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a filter including a housing with multiple flow passages and filter elements, including at least first and second flow passages therethrough including respective first and second filter elements in parallel. Respective internal dividing walls separate flow passages in space saving relation.

U.S. Patent Publication No. 2008/0011673, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a direct flow filter having one or more upstream and/or downstream face seals transversely spanning from one set of pleat tips at least partially towards the other set of pleat tips and laterally spanning adjacent channels.

U.S. Pat. No. 7,879,125, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a filter provided by pleated filter media having a plurality of pleats defined by wall segments extending axially along an axial direction along an axis and extending transversely along a transverse direction between first and second sets of pleat tips at first and second sets of axially extending bend lines. The pleated filter media spans laterally along a lateral span along a lateral direction, with the wall segments being spaced from each other by lateral gaps. The pleats have a pleat depth along the transverse direction along the wall segments between the first and second sets of pleat tips. The pleat depth varies as the pleated filter media spans laterally along the lateral direction.

U.S. patent application Ser. No. 13/002,863, filed Jan. 6, 2011, now U.S. Pat. No. 8,668,759, issued Mar. 11, 2014, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a filter assembly, panel filter element, and servicing method for reducing inlet flow restriction from a housing inlet into an inlet plenum and reducing outlet flow restriction from an outlet plenum to a housing outlet.

SUMMARY

The present disclosure stems from the inventors' research and development of filters and filter media having reduced restriction.

In one example, a pleated filter media extends in an axial direction, a transverse direction that is perpendicular to the axial direction, and a lateral direction that is perpendicular to the axial direction and perpendicular to the transverse direction. The pleated filter media includes a plurality of pleats comprised of pleat segments extending in the axial direction between first and second axial ends and extending in the transverse direction between first and second sets of pleat tips at least partially defined by first and second sets of bend lines. Axial flow channels are defined between the pleat segments in the lateral direction and the plurality of pleats has a width in the transverse direction that varies along the axial direction.

In another example, a method of forming a filter media comprises: folding a sheet of filter media to form a plurality of pleats comprised of pleat segments extending in the axial direction between first and second axial ends and extending in the transverse direction between first and second sets of pleat tips at least partially defined by first and second sets of bend lines such that axial flow channels are defined between the pleat segments in the lateral direction; and forming the plurality of pleats to have a width in the transverse direction that varies along the axial direction.

In another example, a filter for filtering fluid comprises: a housing retaining a pleated filter media; the pleated filter media comprising a plurality of pleats comprised of pleat segments extending in the axial direction between first and second axial ends and extending in the transverse direction between first and second sets of pleat tips at least partially defined by first and second sets of bend lines; wherein axial flow channels are defined between the pleat segments in the lateral direction and wherein the plurality of pleats has a width in the transverse direction that varies along the axial direction.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a filter according to a first example of the disclosure wherein a pleated filter media has varying width.

FIG. 2 is an end view of a filter according to the first example of the disclosure.

FIG. 3 is an end view of a filter according to a second example of the disclosure wherein at least a portion of a pleated filter media has varying width.

FIG. 4 is a cross section of a filter according to a third example of the disclosure wherein a pleated filter media is cylindrical.

FIG. 5 is a cross section of a filter according to a fourth example of the disclosure wherein a portion of a cylindrical pleated filter media has varying width.

FIG. 6 is a perspective view of a filter according to a fifth example of the disclosure wherein a portion of a pleated filter media is curvilinear.

FIG. 7 is an end view of a filter according to the fifth example of the disclosure.

FIG. 8 is a cross section of a filter according to a sixth example of the disclosure wherein a portion of a cylindrical pleated filter media is curvilinear.

FIG. 9 is a cross section of a filter according to a seventh example of the disclosure wherein a portion of a cylindrical pleated filter media is curvilinear.

FIG. 10 is a perspective view of a filter according to an eighth example of the disclosure wherein a portion of a pleated filter media is curvilinear and comprises a seal.

FIG. 11 is a perspective view of a filter according to a ninth example of the disclosure wherein a portion of a pleated filter media is curvilinear and comprises a seal.

FIG. 12 is a cross section of a filter according to a tenth example of the disclosure wherein opposing pleated filter media define a Z-filter arrangement.

FIG. 13 is a cross section of a filter according to an eleventh example of the disclosure wherein opposing pleated filter media define a Z-filter arrangement.

FIG. 14a is a top view of a filter media according to a first method for forming the filter media of the disclosure by folding the filter media along a plurality of bend lines.

FIG. 14b is an isometric view of the filter media according to the first method for forming the filter media of the disclosure.

FIG. 15a is a top view of a filter media according to a second method for forming the filter media of the disclosure by forming, cutting, and bonding the filter media.

FIG. 15b is an isometric view of the filter media according to the second method for forming the filter media of the disclosure.

FIG. 16 is an isometric view of a pleated filter media according to the first and second methods for forming the filter media of the disclosure.

FIG. 17 is a top view of a filter media according to a third method for forming the filter media of the disclosure by folding the filter media along radial bend lines.

FIG. 18 is an isometric view of the filter media according to the third method for forming the filter media of the disclosure.

DETAILED DESCRIPTION

In the present disclosure, certain terms have been used for brevity, clearness and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes only and are intended to be broadly construed. The different apparatus and methods described herein may be used alone or in combination with other apparatus and methods. Various equivalents, alternatives and modifications are possible within the scope of the appended claims. Each limitation in the appended claims is intended to invoke interpretation under 35 U.S.C. .sctn.112, sixth paragraph only if the terms “means for” or “step for” are explicitly recited in the respective limitation.

FIGS. 1 and 2 depict a filter 10 having two pleated filter media 12. The pleated filter media 12 extend in an axial direction x, a transverse direction y that is perpendicular to the axial direction x, and a lateral direction z that is perpendicular to the axial direction x and perpendicular to the transverse direction y. The filter 10 includes end caps 14, 16. Fluid to be filtered flows generally directly axially through the filter 10 from the inlet end 18 to the outlet end 20 as shown by the arrow F. However, the terms “inlet end” and “outlet end” are not intended to be limiting, and fluid may flow in directions other than that described with reference to these Figures, such as oppositely from the end 20 to the end 18.

The pleated filter media 12 is pleated along a plurality of bend lines 22 extending in the axial direction x. The plurality of bend lines 22 comprises a first set of bend lines 22 a and a second set of bend lines 22 b. The first and second sets of bend lines 22 a, 22 b partially define a plurality of pleats 24. The pleats 24 are comprised of pleat segments 26 (shown best in FIG. 2) that extend in the axial direction x between first axial ends 28 a and second axial ends 28 b. The pleat segments 26 also extend in the transverse direction y between a first set of pleat tips 30 a and a second set of pleat tips 30 b. As further described below, the first and second sets of pleat tips 30 a, 30 b are at least partially defined by the first and second sets of bend lines 22 a, 22 b.

The pleat segments 26 define axial flow channels 32 therebetween. (For a more detailed view, see FIG. 16.) In one example, at the inlet end 18, the pleat segments 26 have ends that are alternately sealed to one another to define axial flow channels 32 having open ends at the inlet end 18 and to define axial flow channels 32 having closed ends at the inlet end 18. At the outlet end 20, the pleat segments 26 are oppositely alternately sealed such that if at an inlet end 18, the axial flow channel 32 is closed, it is open at the outlet end 20; and if at the inlet end 18, the axial flow channel 32 is open, it is closed at the outlet end 20. In this way, fluid flows generally axially through the inlet end 18 of the filter 10, through the axial flow channels 32 having open ends at the inlet end 18, crosses laterally (in the z-direction) through the pleat segments 26, and exits through the axial flow channels 32 having open ends at the outlet end 20. Sealing of the plurality of pleat segments 26 is further described in U.S. Pat. No. 7,323,106 and U.S. Pat. No. 7,314,558, both of which are incorporated by reference herein in entirety, and both of which take their description from U.S. Pat. No. 6,482,247, which is also incorporated herein by reference in entirety.

In the example shown in FIG. 2, each of the pleated filter media 12 have a width in the transverse direction y that varies along the axial direction x, such as for example from W1 to W2. More specifically, the first set of bend lines 22 a extend in the axial direction. The second set of pleat tips 30 b extend at an angle a to the axial direction x in the transverse direction y such that the width of the pleats 24 in the transverse direction y varies along the axial direction x, to define a linear portion 34 of the plurality of pleats 24 extending at an angle to the axial direction. The linear portion 34 can be formed by a plurality of sunken pleats interdigitated amongst the pleat segments 26 in the lateral direction y, as will be described further herein below. The linear portion 34 of the plurality of pleats 24 can also be formed by sets of bonded edges extending at an angle from one of the first and second sets of axially extending bend lines 22 a, 22 b as is also further described herein below.

FIG. 2 shows two opposing filter media 12 retained by the end caps 14, 16 each filter media 12 comprising the plurality of pleats 24 comprised of pleat segments 26 extending in the axial direction x between first and second axial ends 28 a, 28 b and extending in the transverse direction y between first and second sets of pleat tips 30 a, 30 b defined at least partially by first and second sets of bend lines 22 a, 22 b. Axial flow channels 32 are defined between the pleat segments 26 in the lateral direction z. The plurality of pleats 24 has a width in the transverse direction y that varies along the axial direction x, such as for example from W1 to W2. Further, each opposing filter media 12 comprises a second set of pleat tips 30 b extending at an angle a with respect to the axial direction x wherein the first sets of bend lines 22 a of each filter media 12 are substantially parallel to the axial direction x such that the opposed filter media 12 define a channel 35 therebetween having a V-shaped cross section along the axial direction x.

Fluid to be filtered flows generally axially in the inlet end 18 as shown by the arrow F. Fluid next flows generally axially into the pleated filter media 12, as shown by the arrows F′, through the axial flow channels 32, generally laterally (in the z-direction) through the pleat segments 26 as described above and as shown by the arrows F″, and generally axially out the outlet end 20, as shown by the arrows F″′. If an end cap 14 covers the outlet end 20, fluid may flow generally transversely (in the y direction) to exit the filter media 12.

The V-shaped cross section of the channel 35 increases the flow area between the two filter media 12 as opposed to traditional filters, due to the included angle 2 a between the filter media 12. Such a configuration results in a lower expansion loss (or decreased pressure drop) within the filter 10. Because the first sets of bend lines 22 a are substantially parallel to the axial direction x, filter 10 with this V-shaped channel 35 is able to utilize the same sized end caps 14, 16 as traditional filters. This means the filter 10 can be integrated into the same housing (not shown) as traditional filters because the dimensions of the filter 10 are the same as those of traditional filters, despite the inclusion of varying pleat depth.

In a third example shown in FIG. 3, the width of the plurality of pleats 24 varies in the transverse direction y at least along a linear portion 34 (here, a first segment 34 a, a second segment 34 b, and along pleat tips 30 b) of the plurality of pleats 24. In this example, as in the example of FIGS. 1 and 2, a second set of pleat tips 30 b extends at an angle a from the axial direction x along the entire length of the pleated filter media 12. A first set of pleat tips 30 a at a first segment 34 b extend at an angle .beta. to the axial direction x. The first set of pleat tips 30 a at a second segment 34 b extend substantially parallel to the axial direction x. In this example, the pleated filter media 12 comprises a linear portion having first and second segments 34 a, 34 b that extend at different angles to the axial direction x, respectively. The filter media 12 is one of at least two opposing filter media 12 retained by end caps 14, 16. Each opposing filter media 12 comprises the second set of pleat tips 30 b oriented at an angle .alpha. with respect to the axial direction x such that the opposing filter media 12 define a channel 35 therebetween having a V-shaped cross section along the axial direction x. For each filter media 12, the first set of pleat tips 30 a are oriented at an angle .beta. with respect to the axial direction x at first segment 34 a and the first set of pleat tips 30 a are substantially parallel to the axial direction x at second segment 34 b.

Fluid flows into the filter generally axially in the direction of arrow F. It enters the filter as denoted by the arrows F then flows through the pleated filter media 12, the pleat segments 26 generally laterally (in the z-direction), and the axial flow channels 32, as described above and shown by the arrows F″. Fluid then exits the filter media 12 generally axially as shown by arrows F′″.

As described above, the V-shaped channel 35 increases the flow area between the two filter media 12 and thus decreases pressure drop. In the same way, the portion 34 a of the plurality of pleats 24 provides for decreased pressure drop as fluid exits the pleated filter media 12. Further, if fluid were to flow in a direction substantially opposite to that shown in FIG. 3, fluid entering the pleated filter media 12 at the portion 34 a would also experience decreased pressure drop. Finally, such a configuration as shown in FIG. 3 allows the filter 10 to fit into a smaller housing (not shown).

FIG. 4 shows a third example of a filter 10 having pleated filter media 12. In this example, the filter media 12 comprises a plurality of pleats 24 having a width that varies in the transverse direction y along the axial direction x. For example, the width of the plurality of pleats 24 varies from W1 to W2. The pleated filter media 12 is cylindrical and defines a central opening 36. The second sets of pleat tips 30 b extend at an angle from one another such that the diameter of the central opening 36 increases along the axial direction x from the first axial end 28 a to the second axial end 28 b of the respective filter media 12. In the example shown, the diameter increases for example from D1 to D2. The central opening 36 is generally V-shaped in cross section along the axial direction x. An end cap 16 is provided at the second axial end 28 b, and although not shown here, an end cap 14 can be provided at the first axial end 28 a as well.

Fluid to the filter flows generally axially in the direction of arrow F, enters the pleated filter media 12 at the arrows F′, flows through the axial flow channels 32 and the plurality of pleat segments 26 generally laterally (in the z-direction) as described above and as shown by the arrows F″, and exits the pleated filter media 12 generally axially as shown by the arrows F″′.

The V-shaped cross section of open area 36 increases the flow area within the cylindrical filter media 12 by making the included angle within the cylindrical filter media 12 bigger than that of traditional cylindrical filter media. This results in decreased pressure drop across the filter such as was described with reference to FIGS. 1-3, and allows use of the same end caps 14 and housing (not shown) as are used for traditional cylindrical filter media.

FIG. 5 shows a cross section of a filter 10 according to a fourth example. In this example, in contrast to the example of FIG. 4, the first set of pleat tips 30 a are not substantially parallel to one another along the entire length of the filter media 12. A second set of pleat tips 30 b extends at an angle to define a central opening 36 that is substantially V-shaped in cross section along the axial direction x. At a first segment 34 a, the first set of pleat tips 30 a extends at an angle .beta. to the axial direction x such that the width of the pleats 24 varies for example from W1 to W2. At a second segment 34 b, the first set of pleat tips 30 a extends substantially parallel to the axial direction x, such that the width of the pleats 24 varies for example from W2 to W3.

Fluid to be filtered flows generally axially in the direction of arrow F, enters the pleated filter media 12 as shown by the arrows F′, flows through the axial flow channels 32 and the pleat segments 26 generally laterally (in the z-direction) as described above and shown by the arrows F″, and exits the pleated filter media 12 generally axially as shown by the arrows F′″. As was described with reference to FIG. 3, the configuration of FIG. 5 reduces pressure drop across the filter media 12 upon exit of the filter media 12 if fluid is flowing in the direction of the arrow F shown in FIG. 5. Likewise, if fluid were to flow substantially oppositely to the direction of the arrow F shown in FIG. 5, it would encounter reduced pressure drop due to the portion 34 a of the plurality of pleats 24 that extends at an angle to the axial direction x.

In the example of FIGS. 6 and 7, the width of the plurality of pleats 24 varies in the transverse direction y at least along a portion of the plurality of pleats 24. The portion of the plurality of pleats 24 comprises curvilinear portions 38 a and 38 b joining one of the first axial ends 28 a and second axial ends 28 b to one of the first set of pleat tips 30 a and second set of pleat tips 30 b, respectively. In the example shown, the width of the pleats 24 remains the same (W1) between the first set of pleat tips 30 a and the second set of pleat tips 30 b along the remainder of the portion of the plurality of pleats 24 that is not one of the curvilinear portions 38 a, 38 b. More specifically, at the inlet end 18, the second set of pleat tips 30 b are joined to the second axial ends 28 b by the curvilinear portion 38 b. At the outlet end 20, the first set of pleat tips 30 a are joined to the first axial ends 28 a by the curvilinear portion 38 a. Thus, in the example of FIGS. 6 and 7, the filter 10 comprises two opposing curvilinear portions 38 a, 38 b joining the first axial ends 28 a to the first set of pleat tips 30 a and joining the second axial ends 28 b to the second set of pleat tips 30 b. In this example, the curvilinear portions 38 a, 38 b are smooth curvilinear portions. Other variations of the example shown in FIGS. 6 and 7 are possible. For example, either the first curvilinear portion 38 a or the second curvilinear portion 38 b could be omitted. Further, the remainder of the pleats 24 that do not comprise one of the curvilinear portions 38 a, 38 b need not remain at width W1 between the first set of pleat tips 30 a and the second set of pleat tips 30 b; rather, the width of the plurality of pleats 24 could vary in the transverse direction y along this remainder portion as well, as shown in FIGS. 1-5. Then, the first sets of axial bend lines 22 a could extend substantially parallel to the axial direction x and to one another such that the size of the end caps 14, 16 and housing (not shown) could remain similar to that of traditional filters.

Another way to describe the example of FIGS. 6 and 7 follows. One of the first and second sets of pleat tips 30 a, 30 b has a first filter media edge section 101 extending axially and a second filter media edge section 102 extending from the first filter media edge section 101 and curved from the axial direction x toward the transverse direction y. The first filter media edge section 101 merges into the second filter media edge section 102 along a continuous non-rectilinear transition. One of the first and second sets of axial ends 22 a, 22 b has a third filter media edge section 103 extending transversely (in the y direction) and a fourth filter media edge section 104 extending from the third filter media edge section 103 and curved toward the axial direction x. The third filter media edge section 103 merges into the fourth filter media edge section 104 along a continuous non-rectilinear transition. The second filter media edge section 102 and fourth filter media edge section 104 merge into each other along a continuous non-rectilinear transition as well. This continuous non-rectilinear transition has been referred to above as curvilinear portion 38 a or 38 b.

Fluid to be filtered enters the filter 10 generally axially in the direction of arrow F, enters the pleated filter media 12 via the arrows shown at F′, flows through the axial flow channels 32 and the pleat segments 26 generally laterally (in the z-direction) as described above and shown by the arrows F″, and exits the pleated filter media 12 generally axially as shown by the arrows F″′. Due to the curvilinear portions 38 a and 38 b, fluid encounters reduced restriction when entering and exiting the filter 10. Compared to traditional filters, the fluid now encounters a smoother entry into (or exit from) the filter 10 due to the lack of sharp 90 degree angled pleat tips 30 a, 30 b. This results in lower pressure drop on entry and exit to and from the filter 10 because fluid takes on an ideal entry path. Thus, one of the first and second sets of pleat tips 30 a, 30 b and one of the first and second axial ends 28 a, 28 b meet at a set of reduced-restriction flow-conductive junctions, the set of reduced-restriction flow-conducive junctions having a fluid dynamic profile configured to reduce pressure drop therealong and provide lower restriction than a sharp 90 degree junction angle of the respective pleat tips 30 a, 30 b and axial ends 28 a, 28 b of the filter media 12.

FIG. 8 shows a cross section of a filter 10 according to a sixth example. In this example, the pleated filter media 12 is cylindrical and defines a central opening 36 of which the diameter D1 remains the same except for at a curvilinear portion 38 a. The width of the plurality of pleats 24 between a first set of pleat tips 30 a and a second set of pleat tips 30 b in the transverse direction y remains constant in the axial direction x until the curvilinear portion 38 a is reached. At the curvilinear portion 38 a, the second set of pleat tips 30 b are joined to first axial ends 28 a. The pleated filter media 12 is held in its cylindrical shape by the end caps 14, 16.

Fluid to be filtered flows generally axially into the filter 10 in the direction of arrow F. Fluid flows through the axial flow channels 32, through the plurality of pleat segments 26 generally laterally (in the z-direction) as described above and shown by the arrows F″, and then exits the filter media 12 generally axially as shown by arrows F″′. In this way, fluid encounters reduced restriction as described above as it enters at the ideal entry-shaped first curvilinear portion 38 a.

FIG. 9 shows a cross section of a filter 10 according to a seventh example. In this example, the width W1 of the pleats 24 does not vary between a first set of pleat tips 30 a and a second set of pleat tips 30 b until a curvilinear portion 38 b is reached. The curvilinear portion 38 b joins the first set of pleat tips 30 a to the second axial ends 28 b. The pleated filter media 12 is cylindrical and defines a central opening 36 having a diameter D1 that remains the same along the length of the filter media 12 in the axial direction x. Although not depicted here, the second set of pleat tips 30 b could be joined to the first axial ends 28 a as well, as shown in FIG. 8.

Fluid to be filtered enters the filter at the inlet end 18 as shown by the arrow F, flows through the axial flow channels 32 and the plurality of pleat segments 26 generally laterally (in the z-direction) as described above and shown by the arrows F″, and exits the filter 10 generally axially as shown by the arrow F″′. Due to the curvilinear portion 38 b, fluid encounters reduced restriction as described above when exiting the filter 10.

FIG. 10 shows an eighth example of a filter 10 similar to the example shown in FIGS. 6 and 7. A second set of pleat tips 30 b and second axial ends 28 b are joined by a curvilinear portion 38 b. In this example however, the filter 10 comprises a seal 40 on the curvilinear portion 38 b. The seal 40 seals off the pleat tips 30 b completely. Sealing off the pleat tips 30 b completely causes fluid entering the filter 10 generally as shown by the arrow F to encounter even more reduced restriction than a filter with a curvilinear portion but no seal due to the combination of the curvilinear portion 38 b and the smooth seal 40 that guide fluid into the V-shaped channel 35. A glue line 41 for each filter media 12 is shown extending at an angle to the axial direction x. The glue line 41 seals off alternating axial flow channels 32 as described above. However, in order to utilize more area within the filter media 12, the glue line 41 could be located more immediately adjacent to the seal 40 and could follow the shape of the seal 40 as well.

FIG. 11 shows a ninth example of a filter 10 that is also similar to the example of FIGS. 6 and 7. A first set of pleat tips 30 a are joined to first axial ends 28 a at a curvilinear portion 38 a. A seal 40 is on the curvilinear portion 38 a. In this example, the inlet end 18 and the outlet end 20 are reversed from previous examples. The seal 40 over the curvilinear portion 38 a reduces the restriction on fluid as it flows into the filter at the inlet end 18 and is guided further toward the pleated filter media 12 as is shown by the arrows F. Fluid then enters the filter media 12 as shown by the arrows F′, flows through the axial flow channels 32 and the pleat segments 26 generally laterally (in the z-direction) as described above and shown by the arrows F″, and exits the pleated filter media 12 and the outlet end 20 generally axially as shown by the arrows F″′.

FIG. 12 shows a tenth example of a filter 10 having a Z filter arrangement. The filter 10 comprises a housing 42 retaining two pleated filter media 12. The Z filter arrangement has an inlet end 18 and an outlet end 20 defined by the housing 42. The pleated filter media 12 are held together by an internal dividing wall 44. The pleated filter media 12 shown in this example both comprise at least one segment 34 a, 34 b of a portion of a plurality of pleats 24 having a set of pleat tips 30 a, 30 b oriented at an angle a with respect to the axial direction x. For example, regarding the lower pleated filter media 12, the first set of pleat tips 30 a extend at the angle a to the axial direction x. Regarding the upper pleated filter media 12, the second set of pleat tips 30 b extend at an angle a to the axial direction x. However, the pleat tips 30 a, 30 b in the upper and lower filter media 12 need not extend at the same angle to the axial direction x. A second set of bend lines 22 b of the lower filter media 12 is substantially parallel to the axial direction x, while a first set of bend lines 22 a of the upper filter media 12 is substantially parallel to the axial direction x. The opposing filter media 12 thus define a Z filter arrangement. Z filter arrangements are further described in U.S. Pat. No. 7,540,895, which is incorporated by reference herein in entirety. The terms “upper” and “lower” are used here only to clarify description of the example shown, and are not intended to be limiting.

Fluid to be filtered flows generally axially into the filter 10 through the inlet end 18 as shown by the arrow F. Fluid enters the pleated filter media 12 generally axially as shown by the arrows F′. Fluid flows through the axial flow channels 32 and the axial pleat segments 26 generally laterally (in the z-direction) as described above and shown by the arrows F″. Fluid then exits the pleated filter media 12 generally axially as shown by the arrows F″′ and finally exits the filter 10 at the outlet end 20 as shown by the arrows F″. In a traditional Z filter arrangement, the area between the surface of the filter media 12 and the inner wall surface 43 of the housing 42 is small and creates a region of high pressure drop. Pressure drop is reduced by increasing the gap between the inner wall surface 43 of the housing 42 and the surface of the lower pleated filter media 12 as is shown for example at G1. Creating the gap G1 is accomplished by varying the pleat width along segment 34 a of the lower pleated filter media 12. Likewise, pressure drop upon exit from the upper pleated filter media 12 is reduced by increasing a gap G2 between the surface of the upper pleated filter media 12 and the inner wall surface 43 of the housing 42. Creating the gap G2 is accomplished by varying the pleat width along segment 34 b of the upper pleated filter media 12.

FIG. 13 shows an eleventh example of a filter 10 having a Z filter arrangement. This example is similar to the example of FIG. 12, except it has curvilinear portions 38 a, 38 b rather than linear segments 34 a, 34 b as shown in FIG. 12. A first set of pleat tips 30 a of the lower pleated filter element 12 are joined to first axial ends 28 a by a curvilinear portion 38 a. A second set of pleat tips 30 b of the upper pleated filter media 12 are joined to second axial ends 28 b by a curvilinear portion 38 b. A second set of bend lines 22 b of lower pleated filter media 12 is substantially parallel to the axial direction x along the length of the filter media 12 and a first set of bend lines 22 a of upper pleated filter media 12 is substantially parallel to the axial direction x along the length of the filter media 12. Other reference numbers in FIG. 13 correspond to those in FIG. 12.

Pressure drop is reduced by the configuration shown in FIG. 13 in much the same way as pressure drop is reduced by the configurations shown in FIG. 12 and FIGS. 6 and 7. Fluid experiences reduced restriction along curvilinear portions 38 a and 38 b and thus pressure drop along the pleated filter media 12 is reduced. Although not shown here, one or more of the curvilinear portions 38 a, 38 b could further comprise a seal 40 such as that shown in FIGS. 10 and 11.

Different methods for forming the pleated filter media 12 will now be described with reference to FIGS. 14a -18. FIG. 14a shows a filter media 46 on which first and second sets of bend lines 22 a, 22 b are formed. The filter media 46 can be folded to faun a plurality of pleats 24 comprised of pleat segments 26 extending in the axial direction x between first and second axial ends 28 a, 28 b and extending in the transverse direction y between first and second sets of pleat tips 30 a, 30 b at least partially defined by first and second sets of bend lines 22 a, 22 b. Axial flow channels 32 are defined between the pleat segments 26 in the lateral direction z such that the plurality of pleats 24 has a width in the transverse direction y that varies along the axial direction x. Although not shown here, the varied width can be accomplished by forming a curvilinear portion joining one of the first and second axial ends 28 a, 28 b to one of the first and second sets of pleat tips 30 a, 30 b, respectively. This example of a pleated filter media 12 is shown in FIGS. 6 and 7. Alternatively, the varied width can be accomplished by joining one of the first and second axial ends 22 a, 22 b to one of the first and second sets of pleat tips 30 a, 30 b, respectively, by a linear portion 34, as shown in FIGS. 1-4.

In one example shown in FIGS. 14a and 14b , the linear portion 34 of the plurality of pleats 24 is formed by a plurality of sunken pleats 48 interdigitated amongst pleat segments 26 in the lateral direction z. The sheet of filter media 46 is folded to form the plurality of sunken pleats 48. The filter media 46 is folded so that the first and second sets of bend lines 22 a, 22 b extend axially and so that each sunken pleat in the plurality of sunken pleats 48 extends inwardly in the transverse direction z from one of the first and second sets of pleat tips 30 a, 30 b so as to form third, fourth, and fifth sets of bend lines 22 c, 22 d, 22 e extending at an angle .theta. to the axial direction x. Each sunken pleat in the plurality 48 comprises sunken pleat segments 26 a, 26 b extending in the transverse direction y between the fifth bend line 22 e and one of the third and fourth bend lines, 22 c, 22 d. For example, sunken pleat segment 26 a is formed between bend lines 22 c and 22 e. Likewise, sunken pleat segment 26 b is formed between bend lines 22 e and 22 d. Each sunken pleat in the plurality 48 thus has a triangular cross section in the axial direction x and in the transverse direction y.

In another example shown in FIGS. 15a and 15b , the linear portion 34 of the plurality of pleats 24 is formed by sets of bonded edges 50 a, 50 b extending at an angle .theta. from one of first and second sets of axially extending bend lines 22 a, 22 b. The sheet of filter media 46 is folded so that the first and second sets of bend lines 22 a, 22 b extend axially. Then the sheet of filter media 46 is cut to form opposing edges 50 a. 50 b of pleat segments 26 extending at the angle .theta. from one of the first and second sets of axially extending bend lines 22 a. 22 b. In the example shown, the opposing edges 50 a, 50 b extend from the second set of bend lines 22 b. Then, the edges 50 a, 50 b are bonded together. This creates pleat segments 26 that have widths that are axially (in the x-direction) and transversely (in the y-direction) coextensive with each other and vary substantially equally in the transverse direction y. The opposing edges 50 a, 50 b can be bonded in many different ways, for example with glue applied along the dashed lines shown in FIG. 15 a.

FIG. 16 shows a close-up view of the folded filter media 12. The filter media 12 has pleat segments 26 and axial flow channels 32. Also shown are first and second sets of bend lines 22 a, 22 b and first and second sets of pleat tips 30 a, 30 b. In the example shown, the first set of bend lines 22 a and the first set of pleat tips 30 a extend substantially parallel to the axial direction x along the length of the filter media 12. A first segment 34 a of the second set of pleat tips 30 b extends at an angle .alpha. to the axial direction x. A second portion 34 b of the pleated filter media 12 has axial bend lines 22 b and pleat tips 30 b that extend substantially parallel to the axial direction x. Thus, the pleat tips 30 a, 30 b are only partially defined by the bend lines 22 a, 22 b, except where the bend lines 22 a, 22 b do not extend axially, or where they are cut to form a linear or curvilinear portion. In this example, a plurality of sunken pleats 48 is also shown. However, as in the example of FIGS. 15a and 15b , the sunken pleats 48 could be removed and the remaining edges bonded together along first and second edges 50 a, 50 b.

FIGS. 17 and 18 depict a third method for forming the pleated filter media 12. A filter media 46 is cut into an arc along the arced lines 52 a and 52 b. The left-over portions (shown hatched) of filter media 46 are discarded. The sheet of filter media 46 is folded back and forth so that first and second sets of bend lines 22 a, 22 b extend radially at angles to the axial direction x. In the example shown, these angles are 6. FIG. 18 shows how folding the filter media 46 in this way results in pleat segments 26 having a width that varies along the axial direction x in the transverse direction y. The width varies for example from W1 to W2. 

What is claimed is:
 1. A pleated filter media extending in an axial direction, a transverse direction that is perpendicular to the axial direction, and a lateral direction that is perpendicular to the axial direction and perpendicular to the transverse direction, the pleated filter media comprising: a plurality of pleats comprised of pleat segments extending in the axial direction between first and second axial ends and extending in the transverse direction between first and second sets of pleat tips, the plurality of pleats including a curvilinear portion that joins one of the first and second axial ends to one of the first and second sets of pleat tips.
 2. The pleated filter media according to claim 1, wherein a width of the plurality of pleats in the transverse direction varies at least along a portion of the plurality of pleats.
 3. The pleated filter media according to claim 1, wherein the curvilinear portion is a smooth curvilinear portion.
 4. The pleated filter media according to claim 1, comprising a seal on the curvilinear portion.
 5. The pleated filter media according to claim 1, wherein the curvilinear portion is one of two opposing curvilinear portions joining the first axial end to the first set of pleat tips and joining the second axial end to the second set of pleat tips, respectively.
 6. The pleated filter media according to claim 1, wherein the portion of the plurality of pleats comprises a linear portion extending at an angle to the axial direction.
 7. The pleated filter media according to claim 6, wherein the linear portion comprises first and second segments that extend at different angles to the axial direction, respectively.
 8. The pleated filter media according to claim 6, wherein the linear portion is formed by a plurality of sunken pleats interdigitated amongst the pleat segments in the lateral direction.
 9. The pleated filter media according to claim 8, wherein the first and second sets of bend lines extend axially and wherein each sunken pleat in the plurality of sunken pleats is bent inwardly in the transverse direction from one of the first and second sets of axially extending pleat tips so as to form first, second, and third sets of bend lines extending in at least one angle to the axial direction.
 10. The pleated filter media according to claim 9, wherein each sunken pleat in the plurality comprises sunken pleat segments extending in the transverse direction between the third bend line and one of the first and second bend lines, and wherein each sunken pleat in the plurality has a triangular cross-section in the axial and transverse directions.
 11. The pleated filter media according to claim 1, wherein at least one of the first and second sets of pleat tips and one of the first and second axial ends meet at a set of reduced-restriction flow-conducive junctions, the set of reduced-restriction flow-conducive junctions having a fluid dynamic profile configured to reduce pressure drop therealong and provide lower restriction than a sharp 90 degree. junction angle of a respective pleat tip and axial end of the filter media.
 12. The pleated filter media according to claim 11, wherein: the one of the first and second sets of pleat tips has a first filter media edge section extending axially, and a second filter media edge section extending from the first filter media edge section and curved from the axial direction toward the transverse direction, the first filter media edge section merging into the second filter media edge section along a continuous non-rectilinear transition; the one of the first and second sets of axial ends has a third filter media edge section extending transversely, and a fourth filter media edge section extending from the third filter media edge section and curved toward the axial direction, the third filter media edge section merging into the fourth filter media edge section along a continuous non-rectilinear transition; and wherein the second and fourth filter media edge sections merge into each other along a continuous non-rectilinear transition.
 13. A method of forming a filter media extending in an axial direction, a transverse direction that is perpendicular to the axial direction, and a lateral direction that is perpendicular to the axial direction and perpendicular to the transverse direction, the method comprising: folding a sheet of filter media to form a plurality of pleats comprised of pleat segments extending in the axial direction between first and second axial ends and extending in the transverse direction between first and second sets of pleat tips; and forming the plurality of pleats to have a curvilinear portion that joins one of the first and second axial ends to one of the first and second sets of pleat tips.
 14. The method according to claim 13, comprising folding the sheet of filter media to form a plurality of sunken pleats interdigitated amongst the pleat segments in the lateral direction.
 15. The method according to claim 14, comprising folding the sheet of filter media so that the first and second sets of bend lines extend axially and so that each sunken pleat in the plurality of sunken pleats extends inwardly in the transverse direction from one of the first and second sets of pleat tips so as to form first, second, and third sets of bend lines extending at an angle to the axial direction.
 16. A filter for filtering fluid, the filter extending in an axial direction, a transverse direction that is perpendicular to the axial direction, and a lateral direction that is perpendicular to the axial direction and perpendicular to the transverse direction, the filter comprising: a housing retaining a pleated filter media; the pleated filter media comprising a plurality of pleats comprised of pleat segments extending in the axial direction between first and second axial ends and extending in the transverse direction between first and second sets of pleat, wherein the plurality of pleats includes a curvilinear portion that joins one of the first and second axial ends to one of the first and second sets of pleat tips.
 17. The filter according to claim 16, wherein the filter media is one of at least two opposing filter medias retained in the housing, each comprising the plurality of pleats comprised of pleat segments extending in the axial direction between first and second axial ends and extending in the transverse direction between first and second sets of pleat tips defined by first and second sets of bend lines; wherein axial flow channels are defined between the pleat segments in the lateral direction; and wherein the plurality of pleats has a width in the transverse direction that varies along the axial direction.
 18. The filter according to claim 17, wherein each opposing filter media comprises at least one set of pleat tips oriented at an angle with respect to the axial direction and wherein the second set of bend lines of one of the filter media is substantially parallel to the axial direction and wherein the first set of bend lines of the other of the filter media is substantially parallel to the axial direction such that the opposed filter media define a Z-filter arrangement.
 19. The filter according to claim 17, wherein each opposing filter media comprises at least one set of pleat tips oriented at an angle with respect to the axial direction and wherein the first set of bend lines of each filter media is substantially parallel to the axial direction such that the opposed filter medias define a channel therebetween having a V-shaped cross section along the axial direction.
 20. The filter according to claim 19, wherein the pleated filter media is cylindrical and defines a central opening having a diameter that increases along the axial direction from the first axial end to the second axial end of the respective filter media. 